Switch structure



March 21, 1950 2,501,456

E. P. THIAS ETAL SWITCH STRUCTURE Filed June 5, 1948 Patented Mar. 21, 195o SWITCH STRUCTURE Edwin P. Thias, Hollywood, and Warren W. White, Altadena, Calif., assignors to Standard Coil Products Co., Inc., Chicago, Ill., a corporation of Illinois Application June 5, 1948, Serial No. 31,358

7 Claims. l

This invention relates to switches and particularly to such switches for use in high frequency electrical systems.

In many high frequency electrical systems such as those embodied in radio or television apparatus, the desired switching is accomplished as to certain of the circuit elements by means of switching units that embody switches having spring elements included in at least one of the contacts of each switch. Where switches of this character are used, the element or contact of the switch that is mounted upon a resilient mounting arm or spring usually requires a substantial degree or range of movement in the course of a switch engaging or disengaging operation, and as a result of this it is necessary to afford a spring element that has a relatively wide range of movement. In many of the locations in which such a switch is to be incorporated in a high frequency electrical system, the switch is included in a circuit that includes an inductance which constitutes one of the circuit elements of the high frequency system. Where the system is designed for operation on relatively high frequencies, the value of the inductances that are to be thus connected into the system by means of the switching mechanism is relatively small, and it has been found that prior switch mechanisms employed in this relationship in a high frequency electrical system have been of such a character as to embody a considerable inductance within themselves, and

this inductance has been of such a value with respect to the value of the inductance or inductances that are to be coupled into the system,

that proper performance has been dilllcult to at- '2.

tain. In view of the foregoing it is an important object of the present invention to enable switching means embodying resilient or spring mounted contacts to be utilized in high frequency electrical systems without causing objectionable variation in effective values of the inductances in the system, and a related object is to afford a switch mechanism in which a spring mounted contact having a wide range of yielding movement may be constructed in such a way that the inductance introduced by the resilient mounting will be extremely small and of such a value that it will not interfere with or change the effective value of the inductive elements of the system that may be related to or governed by such a switch means.

Other and related objects of the present invention are to aord a wide range of movement of the resiliently mounted contact in a switch of the aforesaid character, and to accomplish this through the use of a spring arm of minimum (Cl. 20D-166) 2 overall length. Related objects are to enable the spring mounting of such a contact of a switch to be accomplished in such a way that a novel current path is obtained, and to render such current path effective to cancel a large portion of the inductance created as an incident to the current flow through the spring mounting element. More specifically, it is an object of this invention to afford a resilient mounting spring for switch contacts wherein, for any 'given displacement of the contact, the spring mounting element may be of a substantially smaller length than heretofore required.

Where spring contacts of the aforesaid character are provided, it is customary to guide the contact members through a suitable guiding plate, and to attach one end of e ch contact to the end of a ilat spring that is ut lized to impart a yielding force to the contact to rge the same in one direction through the guiding means of the mounting plate. In attaining the desired range of movement of such a spring contact, it is usually necessary to employ a spring of substantial length, and. as this spring is bent or flexed due to movement of the contact in its guiding plate, the point of attachment of the contact to the springmoves laterally with respect to the axis of the guiding means. This inherent characteristic of spring contact mechanisms as heretofore used has made it necessary to employ relatively loose guiding surfaces for the spring contacts in order to avoid binding, and'in many types of equipment this is considered to be undesirable. It is, therefore, a further and important object of the present invention to enable the resilient forces to be applied to a switch contact by a flat spring in such a wayv that the point of attachment of the contact to the spring member is not shifted transversely of the axis of the guiding means in course of flexure of the spring, and a related object is to enable such spring contact elements to be more accurately guided than has heretofore been possible.

Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which, by way of illustration, show a preferred embodiment and the principles thereof and what we now consider to be the best mode in which we have contemplated applying those principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present 3 invention and the purview of the appended claims.

In the drawings:

Fig. 1 is a transverse cross sectional view taken through a switching unit in which spring contact switches embodying the present invention are employed;

Fig. 2 is a fragmentary view taken from the line 2-2 of Fig. 1;

Fig. 3 is a cross sectional view taken substantially along the line S-S of Fig. 2;

Fig. 4 is a cross sectional view taken substantially along the line 4-4 of Fig. 2;

Fig. 5 is a view similar to Fig. 4 and illustrating the parts in a different relationship;

Fig. 6 is a plan view of the spring element at an enlarged scale and showing the principal elements of the spring disposed in a common plane; and

Fig. 7 is a cross sectional view taken longitudinally through the spring and illustrating the pre-tensioned form thereof before mounting of the spring in the assembly.

For purpose of disclosure herein the invention has been illustrated as embodied in a band switching or selection unit I in which a selecting drum II has a plurality of rows or sets of shiftable switch contacts ISM adapted, by rotative indexing of the drum, to be brought selectively into cooperating relation to a single set of stationarily located spring contacts ISS that are disposed in a row parallel to the rows of contacts ISM. Each row of contacts ISM is allorded as a part of a separately formed unit I4 va plurality of such units I4 being disposed in parallel relation about the periphery of the drum II. Each unit I4 includes a mounting plate I5 of insulating material, and the contacts ISM are generally in the form of rivets extended through the plate I so as to locate the heads of the rivets on the outer face of-the plate I5 while connecting lugs I8. formed as part of the rivets, are disposed on the inner face of the plate I5 for connection with circuit elements such as an inductance coil I'I carried on the inner face of the plate.

As a set or row of contacts ISM is moved into or out of position in alignment with the row of contacts ISS, as between the dinerent positions shown in Figs. 4 and 5, it is essential that these contacts ISS be movable generally radially with respect to the axis of the drum, or in other words, substantially perpendicular to the general path traversed by the contacts ISM in the actual engaging or disengaging operation. Thus each contact ISS is in the form of a rivet in which the head constitutes the actual contact while a stem I 3X of the rivet is slidably extended and guided through a guide bore IS formed in a stationary insulating plate 20. The mounting plate 25 is disposed normal to the desired path of movement of the contact stem ISX, and the guide bores Il yare normal to the faces of the plate 2l s0 that the contacts I SS are thus guided for movement along the desired paths of movement.

`On the outer face of the plate 20, elongated nat springs 25 are mounted on the plate 2li as by rivets 25 and are operatively connected to the outer ends of the respective stems ISX so as to impart an kinwardly acting resilient force urging each contact ISS inwardly or toward the opposed contact ISM. Each spring 25 has terminal lugs 25C formed thereon adjacent to the mounting rivet 2S so that the spring 25 must serve as the to the stem ISX of the contact ISS, and under and in accordance with the present invention the conductive path through the spring 25 is arranged in such a way that the very minimum of inductance is encountered or introduced into the related circuit by reason of -such current path.

In attaining such low inductance in the spring 25. the overall length of the spring is minimized while at the same time 'providing for an adequate range of movement of the contact ISS within the elastic range of the spring 25, and for applying such resilient forces to the stem ISX without appreciable lateral displacement of the connected end of the stem so as to thereby avoid binding of the stem ISX in its guide bore. This is accomplished under the present invention in such a way that the inductance inherent in the current ow along such path through the spring 25 is produced as opposltely acting inductive forces of substantially equal value and in a coupled relation so' as to cancel out the major portion of such inductance and render the same ineffective in the circuit.

Thus in attaining such low inductance and accurate guiding action the spring 25 has a narrow slit 25S of generally U-shaped configuration formed therein with the sides of the U parallel to the sides of the spring 25 and with the open end of the U disposed adjacent to but spaced from the free end 25E of the spring. The

length of the U is such that the closed end of the U is located adjacent to the mounting rivet 26, and the portion of the spring 25 between the closed end of the U and the connecting lug 25C may be termed the mounting portion of the spring 25. 'I'he slit 25S thus serves to deiine an elongated tongue 25T that is integral with the spring 25 adjacent the free end of the spring 25, and this free end of the spring 25 is in effect connected to the mounting portion by parallel arms 25A disposed on opposite sides of the tongue 25T.

The tongue 25T terminates in a contact mounting end at the closed end of the U-shaped slit 25S, and this mounting end has an opening 25M, Fig. 6, through which the reduced or shouldered upper end of the shank ISX may be passed to receive the head ISH which secures the contact ISS operatively to the spring 25.

In the manufacture of the spring 25, the arms 25A and the tongue 25T are in effect pre-tensioned by forming the spring in the shape illustrated in Fig. 7, and hence when the spring is put in place on mounting plate 2l, the arms 25A and the tongue 25T tend normally to lie in a common plane and in contact with the outer face of the plate 2l, as shown in Fig. 5, and the parts of the spring 25 assume this relation when the contactsISM are out of engagement with the contacts ISS. When the contacts ISM are moved toward their engaged relation with respect to the contacts ISS, the rounded surfaces or heads of the opposed contacts engage with a camming action so as to raise the contacts ISS against the resilient forces imposed thereon by the springs 25. As each contact ISS is thus shifted the spring 25 is distorted and placed under tension in what may be termed a compound action so that the required displacement of the contact ISS may be accomplished within the resilient limits of the spring 25 while at the same time allowing a relatively short spring to be used.

As will be evident in Fig. 4. this compound disconductive path from such' connecting lug 25C 75 tortion of the spring 25 involves transmission of ,tongue 25T through the tongue to the free end 25E, and thence through the arms 25A to the mounting portion of the spring. This results in ilexure of the arms 25A so as to separate the free end 25E substantially from the outer face of the plate 20, and at the same time, the tongue 25T is ilexed relative to the free end 25E so that the contact mounting end of the tongue 25T is spaced from the plate in an'amount equal to approximately twice the displacement of the freeend E. In attaining accurate movement of the end of the tongue 25T along the axis of the guide bore without application of lateral forces to the stem ISX, it is important that the arms 25A and the tongue 25T each bend through substantially eoual distances, and this is accomplished by making the total cross sectional area of the two arms 25A substantially equal to the cross sectional area of the tongue 25T. Thus for any required displacement of the contact IIS, the overall length of the spring 25 may be established at slightly more than one-half of the length heretofore required, so as to reduce inductance as such inductance is related to length of the spring. Under the present invention. however. the overall inductance that is rendered effective in the circuit by the-spring 25 is minimized y by reason of the form and relationship of the elements of the spring. for because of this form the current path through the spring from the lug 25C to contact HS includes return bend portions disposed in closely spaced relation so that ecual and opposite currents now in these closely spaced portions of the path, and this is effective to cancel out a substantial portion of the inductance inherent in such current path. Thus such current path extends from the contact HS along the tongue 25T longitudinally thereof and near the free end ISF. this current path divides and passes back along the two arms 25A to the lug 25C. g

From the foregoing description it will be evident that the present invention affords an improved spring contact switch mechanism, and it will be apparent-that under the present invention, the movable or shiftable contact of a switch may be accurately guided without danger of binding of the contact in its guiding or mounting element. It will also be evident that the present invention enables a wide range of springresisted movement to be attained in such-a spring contact switch without introduction of obiectionable inductance in the circuit in which the switch is used.

Thus, while we have illustrated and described the preferred embodiment of our invention, it is to be understood that this is capable of variation and modification and we therefore do not wish to be limited to the precise details set forth, but desire to avail ourselves of such changes and alterations as fall within-the purview of the following claims.

We claim:

l. In a low inductance resilient contact switch mechanism, a pair of contact members adapted for relative engaging movement along a predetermined axis and for relative switch-opening and closing movement along a path substantially normal to said axis, and means supporting said contact members for such relative movement including an elongated flat spring member having means at one end defining a mounting portion, said member 4having an arm extended longitudinally from said mounting portion and terminating in a free end, and having an elongated tongue 6 intergral with said arm adjacent said free end thereof and extending toward said mounting portionat said one end and terminating in a contact-mounting end disposed adjacent said mounting portion, means securing said mounting portion in a fixed position with said spring member substantially normal to said axis and with said contact mounting end disposed on said axis, and one of said contact members being mounted on said contact mounting end of said tongue for relative movement along said axis against the compound resistive forces of said arm and said tongue.

2. In a low inductance resilient contact switch mechanism, a pair of contact members adapted for relative engagingmovement along a prede- `termined axis and for relative switch-opening and closing movement along a path substantially normal to said axis, and means supporting said contact members for such relative movement including an elongated fiat spring member having means at one end deiining a mounting portion, said member having a first portion extending longitudinally from said mounting portion and terminating in a free end, and having tongue portion integral with said first portion adjacent said free end thereof and extending toward said mounting portion atl said one end and terminating in a contact-mounting and disposed adjacent said mounting portion, means securing said mounting portion in a fixed position with said t spring member substantially normal to said axis and with said contact mounting end disposed on said axis, and one of said contact members being mounted on said contact mounting end of said tongue portion for relative movement along said axis against the compound resistive forces of said arm and said tongue, said iirst and second portions being of substantially equal strength insofar as resistance to bending is concerned so as to thereby enable axial displacement of said one contact member without lateral displacement thereof relative to said axis.

3. In a low inductance resilient contact switch mechanism, an insulating mounting plate having a guide opening therethrough, a first contact disposed on one side of said plate and having a mounting stem slidably guided in said guide opening for engaging movement of said first contact along a predetermined axis, a second contact mounted for relative switch-opening and closing movementv with respect to said first contact along a path substantially normal to said axis, an elongated ilat spring member having means at one end defining a mounting portion, said member having agenerally U-shaped slit formed therein longitudinally thereof and defining an elongated tongue integral with said member adjacent the other end thereof and extending toward said one end and terminating in a contact-mounting end disposed adjacent said mounting portion, means securing said mounting portion in a fixed position against the other face of said plate with said `spring member substantially normal to said axis and with said contact mounting end disposed on said axis, and said stem of said rst contact being fixed to said contact mounting end of said tongue so that said rst contact is resiliently urged along said axis by the compound resilient action of said member and said tongue.

4. In a low inductance resilient switch contact, an elongated flat spring member having means at one end defining a. mounting portion, said member having a generally U-shaped slit formed therein longitudinally thereof and deiining an elongated tongue integral with said member adjacent the other end thereof and extending toward said one end and terminating in a contactmounting end disposed adjacent said mounting portion, and a contact element mounted on said contact mounting end of saidtongue for displacement substantially perpendicular to the plane of said member against the compound resistive forces of said member and said tongue.

5. In a low inductance resilient contact switch mechanism, a pair of contact members adapted for relative engaging movement along a predetermined axis and for relative switch-opening and closing movement along a path substantially normal to said axis, and means supporting said contact members for such relative movement including an elongated iiat spring member having means at one end deiining a mounting portion, said spring member having a narrow and generally U-shaped slit formed therein longitudinally thereof and defining an elongated tongue integral with said spring member adjacent the other end thereof and extending toward said one end and terminating in a contact-mounting end disposed adjacent said mounting portion, means securing said mounting portion in a ilxed position with said spring member substantially normal to said axis and with said contact mounting end disposed on said axis, and one of said contact members being mounted on said contact mounting end of said tongue vfor relative movement along said axis against the compound resistive forces of said member and said tongue.

6. In a mounting member for a low inductance resilient switch contact, an elongated ilat spring member having means at one end deilnlng a mounting portion, said member having a generally U-shaped slit formed therein longitudinally thereof and defining an elongated tongue integral with said member adjacent the other end thereof and extending toward said one end and terminating in a contact-mounting end disposed adjacent said mounting portion, the portions oi' said member disposed on the outer sides of said slit constituting spring arms, said slit being relatively narrow and the transverse cross sectional area oi' said tongue being substantially equal to the combined transverse cross sectional area of the two arms.

7. A contact mounting element for use in a low inductance resilient switch mechanism, said contact mounting element comprising an elongated iiat spring member having means at one end defining a mounting portion, said member having a narrow and generally U-shaped slit formed substantially centrally therein and extending longitudinally thereof, an elongated tongue positioned within said slit and integral with said member adjacent the other end thereof, said tongue extending toward said one end and terminating in a contact-mounting end disposed adjacent said mounting portion, and a contact element mounted on said contactmounting end of said tongue for displacement of said contact mounting end perpendicular to the plane of said member against the compound resistive forces oi' said member and said tongue.

EDWIN P. THIAS.

WARREN W. WHITE.

REFERENCES CITED The`following references are of record in the ille loi this patent:

UNITED STATES PATENTS Number Name Date 2,068,093 Teriensen Jan. 19, 1931 2,454,060 Hegy Nov. 16, 1948 

